REPTILES OF BOTSWANA

Nile crocodile
Crocodylus niloticus
The nile crocodile is Botswana's largest reptile, reaching lengths of nearly 20 feet and weighing well over a ton!  They are equipped with extremely powerful jaws and prominent teeth. 

Crocodiles are one of the earth's longest living animal, up to and perhaps more than 100 years, and they have changed very little in the last 65 million years. 

They are well designed for living in the water.  Their nostrils and eyes are situated on the tops of their heads, allowing them to appear almost invisible just beneath the water's surface.  Their skin is covered with plates which are very tough and the plates on the top of their head are fused to their skull.  They have webbed hind feet and their powerful tail, which they use for locomotion in the water, measures 40% of the total body length.

Adult crocodiles feed on fish, particularly barbel (catfish), but they also ambush various prey coming to drink at the water's edge.  Small antelopes are the most common such prey, but baboons, monkeys and larger prey such as zebra may also be killed.  Prey is seized with their powerful jaws, whose power exists in the muscles that close the jaw only.  Larger prey is dragged under the water and drowned and then torn in pieces and swallowed without any chewing.  Cooperative feeding does occur on very large items such as a dead hippo; one individual will grab hold while others bite and spin like a piston on their long axis to rip off pieces.

Attacks on humans in Africa are fairly common, though far less so in Botswana than in some other countries due to the lower human population existing in the crocodile's habitats in Botswana.  It is often said that hippos are responsible for the most human fatalities in Africa annually; however, there are some who believe it is actually crocodiles, the difference being that the crocs do not leave behind a body, the person, and any evidence of what happened, just disappears.

Female crocodiles are very attentive mothers.  After laying a clutch of eggs in a sandy pit which she excavates with her feet, the eggs are covered and vigilantly guarded against any and all predators.  The female will not eat during the incubation period, but will return to the water to drink and regulate her temperature as needed. 

As the eggs begin to hatch under the sand, the babies' cries are heard by their mother while they are still breaking out of their eggs.  She carefully digs open her nest to uncover the hatchlings.  The young are picked up delicately, five or ten at a time, in her huge mouth, and shuttled to the shallow water and out of immediate danger.  The young will remain in this safe and calm water area and under their mother's protection for another 6 to 8 weeks.  A female crocodile will use the same nesting spot throughout her entire life.  The sex of the offspring is determined by the temperature at which the egg is incubated; females at 26-30 degrees C and males at 31-34 degrees C.

Crocodiles are present in the waterways of the Okavango Delta, as well as in the Linyanti/Kwando river system and in the Chobe river.  In Botswana crocodiles are only present in large concentrations in the "Panhandle" of the Okavango Delta, their preferred breeding area.  Crocodiles lay their eggs on the Panhandle's sandy shores between September and January, when water levels are lower.

Water monitor lizard
Varanus niloticus
The water monitor is Botswana's largest lizard, attaining lengths of 2 to 3 feet, not including their tail and almost 8 feet in total length.  It has a stout body and well-developed limbs with strong claws.  Their skin is tough, with scales like small beads. 

Like all monitors, they have a long, flexible neck with a long, smooth, retractile, forked tongue, like a snake's.   Adult coloration is olive-brown with 6-11 yellow bands or spots laterally on the body and 10 or more pale cross bands on the tail.

The water monitor lives along major rivers or other permanent waterways and forages for food along the marginal vegetation or in freshwater pools or inundated floodplains.  They are especially fond of eggs and will excavate the nests of terrapins and unattended crocodile nests for their eggs.  They will make efforts to raid bee-eater nests built into the vertical sandy river banks.  Their diet also includes frogs, fish, crabs, and birds.  Adults' teeth are rounded like pegs and are ideal for crushing crustaceans, unlike the sharp, recurved teeth of juveniles.

Water monitors are often seen basking on rocks, sandy river banks or floating mats of vegetation on the water.  When disturbed, they dive into the water and swim below into the safety of reed beds.  If cornered, they will attack by biting and lashing with their tail.  Their major predators are crocodiles and pythons.

Females excavate nests in a living termite mound and lay 20-60 eggs over the course of 2 to 3 days.  The termites repair the hole in their nest and the monitor's eggs are incubated inside at a constant temperature and humidity.  The hatchlings emerge after up to one year in the nest.  Hatching takes place in the summer after the rains have arrived.  The hatchlings dig themselves out of the rain-softened mound together.

Rock monitor lizard
Varanus albigularis
The rock monitor is the land-based cousin of the water monitor.  It also reaches lengths over 2 feet, excluding their tail and over 5 feet in total length.  Like its cousin, it has powerful limbs and sharp claws, with bead-like scales and very tough skin.

Their coloration is dark brown with 5-6 light brown blotches and the tail alternates with bands of dark and light brown.

Rock monitors live in tunnels which they excavate beneath rock overhangs or in abandoned animal burrows.  They are also known to occupy holes in trees.  They are typically solitary and hibernate during the colder winter months.  They are reported to have enormous ranges up to 28 square kilometers.

Their diet consists mostly of invertebrates, but it will kill and eat any small animal which it can overpower and swallow.  They also scavenge on carrion and will often eat young tortoises or snakes.  Rock monitors are fierce when threatened; they will adopt a sideways posture and lash out at their attacked with their long tails.  When it bites, it holds on with a death grip and does not let go.

Females lay eggs in a live termite mound like the water monitor, but usually they a hole dug into soft soil or sand.  The eggs take up to six months to hatch and hatchlings emerge on their own.  Many of the young or eggs fall prey to the banded mongoose.  Martial eagles and the honey badger are the main predators on adult lizards.

Southern African python
Python natalensis
Botswana's largest snake is the southern African python.  Fossils from this family of snakes, which includes boas and pythons, exist as far back as 100 million years ago.  Pythons are constrictors - that is, they kill by coiling tightly around their prey and squeezing tighter and tighter until it suffocates.

All pythons lay eggs and the female coils around them to keep them warm for proper incubation.  Pythons have pits along their lips which detect infrared radiation; this is how they are able to see warm-blooded animals in darkness or even if they are blind.

Southern African pythons have many heat-sensitive pits on both their upper and lower lips.  They have a distinctive "spear-shaped" insignia on the top of their head.   Their body is grey-brown or slightly greenish with dark-brown, black-edged markings along its back.  They have very small body scales.

P. natalensis often basks in the sun and they love the water, often using it to hunt.  They may dive deep into ponds or channels and stay submerged for long periods.  They ambush their prey, usually at dusk or in darkness.  Adults eat small antelopes, monkeys, monitor lizards and sometimes crocodiles.  Pythons are capable of swallowing very large prey, much larger than the width of their jaws and body.  They accomplish this by dislocating their jaws before they begin to swallow their prey, allowing their mouths to stretch around prey much larger than their head.  Pythons may fast for extended periods between feedings.

Females lay 30 to 50 eggs in abandoned aardvark burrows or termite mounds and incubates her young by coiling around the eggs.  The young hatch in 65-80 days.

Pythons lunge and bite if threatened.  They have very large teeth and are capable of inflicting a serious and painful, ripping wound.  They are one of the world's only snakes which are large enough to kill a man (and eat one).  Human fatalities have been recorded.